The first film chronicles the defense against a siege at a passageway to more lustrious lands. Much like Thermopylae (without the ocean), the defense is for a pass between two great mountains against an evil force. Beyond this pass is...well...the rest of civilization. If the siege can be quelled at this place, then the rest of the land can have time to muster its force and counterstrike. The pass is perpetually guarded by a great fortress led by a dying king. One of his two sons is very loyal, and will defend the fortress in the name of his kin. The other is exiled, because, in a Jacob/Esau type thing, the other stole the first son's birthright to a great blessing by their patron god. This makes him very powerful and formidable. He now lives in the forest and rules a tribe there. Towards the beginning, the great king dies on the brink of war. The evil forces have mustered and are ready to attack the pass. The loyal son spends much time trying to gather many to defend the pass, including his own brother, who he has not spoken to for a long time.
Wow, that's a lot already. Didn't even finish with the first film! It seems like so little in my head. I'll write more later.